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Diffstat (limited to 'gfx/skia/skia/src/utils/SkMatrix22.h')
-rw-r--r-- | gfx/skia/skia/src/utils/SkMatrix22.h | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/gfx/skia/skia/src/utils/SkMatrix22.h b/gfx/skia/skia/src/utils/SkMatrix22.h new file mode 100644 index 0000000000..c8bcd5f6bd --- /dev/null +++ b/gfx/skia/skia/src/utils/SkMatrix22.h @@ -0,0 +1,31 @@ +/* + * Copyright 2014 Google Inc. + * + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + */ + +#ifndef SkMatrix22_DEFINED +#define SkMatrix22_DEFINED + +#include "include/core/SkPoint.h" + +class SkMatrix; + +/** Find the Givens matrix G, which is the rotational matrix + * that rotates the vector h to the positive hoizontal axis. + * G * h = [hypot(h), 0] + * + * This is equivalent to + * + * SkScalar r = h.length(); + * SkScalar r_inv = r ? SkScalarInvert(r) : 0; + * h.scale(r_inv); + * G->setSinCos(-h.fY, h.fX); + * + * but has better numerical stability by using (partial) hypot, + * and saves a multiply by not computing r. + */ +void SkComputeGivensRotation(const SkVector& h, SkMatrix* G); + +#endif |